1. Technical Field
This invention relates to methods and apparatus for tying down buildings against the destructive wind force of hurricanes and the like and, more particularly, in a building having a roof with multiple spaced rafters sitting on side walls, to apparatus for holding the roof on the side walls both vertically and horizontally during high side wind forces comprising, a plurality of roof anchors carried by respective ones of opposite ends of adjacent rafters along a length of the roof; a plurality of ground anchors disposed at respective ones of ends of the rafters opposite the opposite ends carrying the plurality of roof anchors; and, a plurality of straps connected between respective ones of the plurality of roof anchors and the plurality of ground anchors.
2. Background Art
Property loss from hurricanes can be substantial as the residents of Florida and Hawaii found out recently. Unless homes are constructed in a way to resist the forces created on and in them by hurricane force winds as depicted in FIG. 1, they can be completely destroyed. Roofs are lifted completely off as depicted in FIG. 2 and/or walls are flattened to the ground as depicted in FIG. 3. Unfortunately, very few homes and similar buildings in existence in hurricane vulnerable areas are built with adequate provision for resisting such forces.
Stand-alone devices such as airplanes and mobile homes have used tie-down systems against gale force winds for a long time. Because of their manner of construction, straps passing over them and fastened to ground anchors typically work adequately for the purpose. Trying to adapt these prior tie-down systems to homes and similar buildings doesn't work because of the difference in construction. As depicted in FIG. 4, a house 10 has walls 12 and a roof 14. Typically, the roof 14 is of a generally unitary construction having a plurality of rafters joined by roof sheathing covered by some sort of a water-resistive covering such as shingles. The roof simply sits on the top edges of the walls 12 and is held in place mostly by gravity and some nails "toe-nailed" in place. In some cases, small metal clips are employed in lieu of the toe-nails. To provide hurricane protection, the roof rafters are bolted to the walls at their point of contact using steel plates and straps. The problem to be described with respect to FIGS. 4 and 5 can even occur with the bolting process, however, for reasons which will become apparent.
As depicted in FIG. 4, one prior art method of attempting hurricane protection is to use strap or cable tie-downs 16 connected from the ends 18 of the rafters to a ground anchor 20. When subjected to the hurricane force winds 22 of FIG. 1, two types of forces are created in the house 10. First, there is a lifting force 24 on the roof 14 created by the winds 22 passing over the roof, which acts as an airfoil. For the same reason a 747's wings lift it into the air, the roof 14 wants to lift the house 10. Second, because the ends 18 of the rafters are connected to the ground anchors 20, there is a force 26 tending to pull the roof 14 apart at its ridge line 28. As a result, the roof 14 can pull apart and lift off as depicted in FIG. 5. Once the roof 14 is gone, the walls 12 can be blown down as in FIG. 3.
Using the continuous strap approach of mobile homes and airplanes as depicted in FIG. 6 where a plurality of straps 30 pass over the roof 14 between ground anchors 20 doesn't work because of the manner of construction of a house. What happens is depicted in FIG. 7. While it is true that the straps 30 prevent the roof 14 from being blown off, they don't prevent the walls 12 from being blown over. The roof 14 simply slides sideways within the straps 30 as the walls 12 go over. At the very least, the house 10 remains as in FIG. 7 and is rendered uninhabitable. At worst, the roof 14 ends up sitting on a pile of rubble that was once the walls 12.
Wherefore, it is an object of this invention to provide a home or other building of similar construction with a way of successfully resisting hurricane force winds.
It is another object of this invention to provide a home or other building of similar construction with a way of successfully resisting hurricane force winds which can be deployed only when there is a danger imminent.
It is still another object of this invention to provide a home or other building of similar construction with a way of successfully resisting hurricane force winds which can be deployed quickly and easily when there is a danger imminent.
It is yet another object of this invention to provide a home or other building of similar construction with a way of successfully resisting hurricane force winds which creates compressive forces within the structure and resists sideward sliding forces on the structure.
Other objects and benefits of this invention will become apparent from the description which follows hereinafter when read in conjunction with the drawing figures which accompany it.